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Old 31-01-2012, 04:37   #16
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Re: Portable AIS

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Originally Posted by janp391 View Post
Maybe this is the solution.
Belfield Software - USB GPS & AIS Dongle
Woo, what a find! It even outputs NMEA 0183 VDM messages, which means you can have you own boat "seen" by AIS-capable boats/ships, and maybe its name plotted if the software supports it (OpenCPN plug-in?). The software delivered with the dongle appears to be Windows only though. Finding/writing a Linux/Mac driver for the dongle may be tricky - I'll be happy to learn othervise.
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Old 31-01-2012, 04:44   #17
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Re: Portable AIS

John...
It's the AIS receiver from Radar Gadgets - ADS-B aircraft radio receiver - Virtual Radar - The USB interface uses a standard FTDI chip - no special driver needed for Linux or Mac - NMEA sentences on the output, so no special client software is needed - Anything that understands AIS NMEA sentences can be used.

Pavel
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Old 31-01-2012, 04:54   #18
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Re: Portable AIS

Are there any reports about sensitivity?
And it is a 1 channel receiver "listening on Channel A or B or alternating". This will decrease reception a bit as well - but will not be critical depending on the application.

Hubert
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Old 31-01-2012, 05:50   #19
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Re: Portable AIS

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Originally Posted by janp391 View Post
Maybe this is the solution.
Belfield Software - USB GPS & AIS Dongle
Nice, but pricey for a single-channel receiver.

Here's another:

Comar Systems AIS-2-USB

It's dual channel but also a bit expensive. It's available in the US for $350 from Milltech Marine. I think you have to supply your own antenna as well.

Just keep Googling "usb ais receiver" every few days. New products are coming on line fast in this area.

Fabbian
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Old 31-01-2012, 06:59   #20
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Re: Portable AIS

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Originally Posted by Skipper Solo View Post
It even outputs NMEA 0183 VDM messages, which means you can have you own boat "seen" by AIS-capable boats/ships...
I think you misunderstand what this device is going to do. It outputs NMEA to your computer. It does not output it through a transmitter. It is a receiver ONLY. Nothing gets transmitted, so no other boats are going to be able to see your boat.

Still, it's a great little device for those who want to receive AIS signals and plot them on their computer. And because it does provide an NMEA stream, you could connect your computer to the onboard NMEA network (if you have one) and feed the AIS signals to a chartplotter or radar screen.
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Old 31-01-2012, 10:28   #21
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Re: Portable AIS

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Originally Posted by bcn View Post
Are there any reports about sensitivity?
And it is a 1 channel receiver "listening on Channel A or B or alternating". This will decrease reception a bit as well - but will not be critical depending on the application.

Hubert
The only testing I've done so far was with an antenna cannibalized from a handheld VHF, glued to the portlight and in an are with limited traffic - could see targets about 2.5 miles distant. I will do some testing with a masttop antenna next time I will be on the boat - there's a Comar CSB-200 there so I should have a decent comparison at hand...

Pavel
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Old 31-01-2012, 12:37   #22
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Re: Portable AIS

Quote:
Originally Posted by denverd0n View Post
I think you misunderstand what this device is going to do. It outputs NMEA to your computer. It does not output it through a transmitter. It is a receiver ONLY. Nothing gets transmitted, so no other boats are going to be able to see your boat.

Still, it's a great little device for those who want to receive AIS signals and plot them on their computer. And because it does provide an NMEA stream, you could connect your computer to the onboard NMEA network (if you have one) and feed the AIS signals to a chartplotter or radar screen.
Indeed, discovered that after I had posted this (and sent off an email to the seller for clarification wether it is a receiver or a transceiver). Still learning...

(Following other AIS discussions here, it appears to be regarded as a useful tool, partly overlapping but not replacing radar. Nice to have AIS transmitting ability as well, with an off-switch.)
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Old 31-01-2012, 12:48   #23
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Re: Portable AIS

I have read different accounts about the importance of receiving both channels. Some websites say its critical to receive both simaltanously others that receiving just one his find because the transmitters automatically switch back and fourth and then a third opinion is that switching back and fourth is bad because you may miss transmissions. Does anyone know for sure? I am inclined to go with a single channel to save money, if the only difference is a small delay in updates.
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Old 01-02-2012, 03:24   #24
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Re: Portable AIS

I'm curios to see test from Pavel, as he will be able to tell us in which frequency the receiver alternates the two frequencies. I read about a system that switched every 6 minutes.
If you combine this with a not so optimal antenna you might find some target close to you before it appears on screen.

We are using a em-trac B100 transponder. The receiver only version is at the market for 210Ä incl. VAT. These are dual channel units with NMEA0183, NMEA2000 and USB. External power though.

With an antenna at 2m height we receive bigger ships (AIS class A, 12W) at +30 nm and class B targets (2W) still a +10nm. Depends on the targets antenna position of course as well.

Hubert
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Old 01-02-2012, 04:58   #25
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Re: Portable AIS

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I read about a system that switched every 6 minutes.
If you combine this with a not so optimal antenna you might find some target close to you before it appears on screen.
6 minutes is the time between transmitting static messages for Class A and B, so if this is lost, yes - next chance will be in 6 minutes again...

But the target, with just the dynamic data, will be seen well before that ... even if a couple of Class B dynamic reports are missed at every 3 minutes - this is only for vessels moving at less than 2 kts, so not really coming close very fast. The other transmissions are being repeated in seconds.

A comprehensive guide at Ais Receiving Station reports a miss rate for single-channel vs. dual channel receiver at 30% of messages with about 25 moving ships nearby.
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Old 02-02-2012, 07:44   #26
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Re: Portable AIS

Thank you everyone for their ideas. I think I will keep searching, it does seem like new products are emerging everyday. I will let you know what I come up with and how well it works.
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Old 07-02-2012, 10:24   #27
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Re: Portable AIS

Regarding the 12' limitation of a USB cable. There are powered USB cables(powered from the USB port) that result in no power loss enabling us to string as many USB cables together as we want without any power loss.
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